Overview

The Electronic Systems group contains all skills related to offensive Electronic Warfare. Some of the skills here are specialized skills which are only useful for a limited selection of pilots. Any skillbooks that cost 3.5 million ISK or less qualify for The Skillbook Program.

Propulsion Jamming, which lets you operate tackling modules, is in a sense the cornerstone of PvP -- you can't kill someone if you can't stop them from warping away.

Level I allows you to fit a prototype cloak, which will let you remain hidden and undetectable by probes in a safespot for as long as you like. Level III lets you use the T2 cloaking device, which is necessary for the MWD+cloak trick, a useful technique for travelling safely through low-sec. Level IV lets you use the CovOps cloaking devices which will let you warp while cloaked, but can only be used on a limited range of stealth ("covert ops") ships. Most combat pilots can probably get away with only training to level I, while haulers should train to level III, and stealth specialists (who want to fly covert ops ships) need level IV.

Target Breaker Amplification

Improves the continuous reflection of active target spectrum breakers, resulting in much improved defenses against all those who wish to target any vessel in the vicinity.
Reduces duration time and capacitor need of Target Spectrum Breakers by 5% per level.

Tracking disruption is the Amarr form of EWAR, and some of their ships have bonuses for it. It can also be useful even when used without hull bonuses, however, particularly for speed tanking or kiting fits, so PvP pilots may want to put some SP into it even if they don't fly Amarr.